The present invention relates to recovery of crude petroleum from subterranean formations. Particularly, it relates to a process for recovering crude petroleum from consolidated or unconsolidated subterranean formations wherein mixtures of steam and petroleum fractions containing naturally occurring phenolic compounds and/or carboxylic acid compounds, and which petroleum fractions are volatile in the presence of steam at injection pressures, are injected into said subterranean formations via injection wells, and wherein produced crude, steam condensate, and injected petroleum fractions are recovered from wells producing from the same subterranean formations.
It is known, generally, to produce petroleum oils, tar sand bitumen, and related petroleum hydrocarbons from shale, sandstone, unconsolidated sand, limestone, and other subterranean formations by injecting steam into a first well for heating the petroleum in such formations and forcing such petroleum to a second well from which such petroleum is produced. Such processes are particularly useful for recovering heavy crudes (low API gravity) and bitumens wherein the heat of said injected steam, when imparted to the crude petroleum, reduces the petroleum viscosity and thereby increases mobility. In this method of recovering heavy petroleum from subterranean formations, a bank of petroleum may build up in a cold zone ahead of the advancing steam. This bank of petroleum restricts flow through the subterranean formation, requiring high pressures for moving the petroleum to the producing well.
An improvement to the process of recovering petroleum employing steam injection was proposed in U.S. Pat. No. 2,862,558, granted Dec. 2, 1958 to Henry O. Dixon. In Dixon, a vapor mixture of superheated steam and a normally liquid hydrocarbon solvent are injected, via an injection well, into a subterranean formation for forcing petroleum to a second well from which petroleum is produced. The hydrocarbon solvents contemplated by Dixon are those which, when admixed with petroleum, reduce the viscosity of the mixture considerably below that of the petroleum in place, thus increasing mobility of the mixture through the subterranean formation. Such solvents ordinarily have the characteristics of such liquids as kerosine, gasoline, jet fuel, stoddard solvent, benzene, xylene, toluene, etc.
Another improvement to the process of recovering petroleum employing steam injection was proposed in U.S. Pat. No. 4,119,149, granted Oct. 10, 1978 to Wu, et al. In Wu, et al, the process comprises flashing a mixture of steam condensate and crude petroleum from a production well for production of a liquid petroleum phase and a vapor phase comprising steam and hydrocarbon vapor, condensing said vapor phase for recovery of said flashed hydrocarbon as a liquid; and injecting said recovered hydrocarbon with additional steam, via an injection well, into said subterranean formation for recovery of additional crude petroleum. In this process, the injected hydrocarbon serves to reduce the viscosity of crude petroleum when admixed therewith.